In modern communication systems, there is an ever-increasing demand for smaller and more versatile portable wireless terminals, e.g., hand-portable telephones. It is well known that the size of an antenna is a critical factor for its performance. Further, the interaction between the antenna, the telephone body and the close-by environment, such as the user, will become more important as the wireless terminals become smaller and smaller. It is thus a formidable task to manufacture such compact and versatile terminals, which exhibit good antenna performance under a variety of conditions.
In current manufacturing of hand-portable telephones, the antenna is commonly adapted to the characteristics of the specific telephone and to be suited for a default use in a default environment. This means that the antenna cannot later on be adapted to any specific condition under which a certain telephone is to be used.
The radiating properties of an antenna device for a portable telephone depends heavily on the shape and size of the support structure such as a printed circuit board (PCB) of the telephone and of the telephone casing. All radiation properties, such as resonance frequency, radiation pattern, polarization, impedance and bandwidth are a product of the antenna device itself and its interaction with the PCB and the telephone casing. Thus, all references to radiation properties made below are intended to be for the whole device in which the antenna is incorporated.
What has been stated above is true also with respect to other communication devices, such as cordless telephones, telemetry systems, wireless data terminals, etc. Thus, the antenna device of the invention is applicable on a broad scale in various communication devices.